Track belt tension management system

Abstract

A track belt tensioning management system is provided for actively adjusting the tension on a track belt in response to the difference in linear output speed between a drive wheel and the track belt. This is accomplished by sensing the speeds of the drive wheel and the track belt and delivering the sensed signals to a controller which processes the signals and determines the difference in their respective linear output speeds. If the difference varies from a predetermined value, the controller directs appropriate signals to a hydraulic valve arrangement which controllably directs pressurized fluid to and from a hydraulic actuator arrangement to adjust the tension between the drive wheel and the track belt. The subject arrangement maintains sufficient frictional force between the drive wheel and the belt to control the slip therebetween as required while at the same time limiting the forces in order to reduce premature failures and/or wear on the track belt and other associated components.

We claim: 
     
       1. A tension management system mounted to a machine having a friction drive between a drive wheel of the machine and a track belt, a source of pressurized fluid, a reservoir, a frame assembly, and a hydraulic actuator arrangement acting through an idler wheel to tension the track belt with respect to the friction drive wheel, wherein the tension management system comprises: a first sensor operative to sense the speed of the drive wheel;   a second sensor operative to sense the speed of the track belt;   a third sensor operative to sense the operating pressure in the hydraulic actuator arrangement;   a hydraulic valve arrangement connected between the source of pressurized fluid, the hydraulic actuator arrangement, and the reservoir; and   a controller operative to receive the sensed speeds of the drive wheel and the track belt and determine their respective linear output speeds sand deliver control signals to the hydraulic valve arrangement to control the tension of the track belt on the drive wheel in response to the difference in linear output speed between the drive wheel and the track belt changing from a predetermined value.   
     
     
       2. The tension management system of claim 1 wherein the hydraulic actuator arrangement includes a hydraulic cylinder arrangement connected between the frame assembly and the idler wheel and the hydraulic valve arrangement includes a control valve operative to proportionally control the flow of pressurized fluid through a supply conduit to one end of the hydraulic cylinder arrangement. 
     
     
       3. The tension management system of claim 2 wherein a pilot operated check valve is disposed in the supply conduit between the hydraulic valve arrangement and the hydraulic cylinder arrangement and an orifice is disposed in a drain conduit connected between the reservoir and a point on the supply conduit between the hydraulic valve arrangement and the pilot operated valve. 
     
     
       4. The tension management system of claim 3 wherein the control valve is an electrically actuated control valve and an accumulator is connected to the hydraulic cylinder arrangement and in fluid communication with the one end of the hydraulic cylinder arrangement. 
     
     
       5. The tension management system of claim 4 wherein the pilot operated check valve has a pilot stage and a second electrically actuated control valve is disposed between the source of pressurized fluid and the pilot operated check valve and operative to communicate the source of pressurized fluid to the pilot stage of the pilot operated check valve. 
     
     
       6. The tension management system of claim 5 wherein the second sensor is sensing the speed of the track belt by sensing the speed of the idler wheel. 
     
     
       7. The tension management system of claim 5 wherein the second sensor is sensing the speed of the track belt by sensing the speed of the machine relative to the surface being traversed. 
     
     
       8. The tension management system of claim 5 wherein the machine includes a second drive wheel, a second idler wheel, and the hydraulic actuator arrangement includes a second hydraulic cylinder arrangement operatively connected between the frame assembly and the idler wheel and the tension management system includes a fourth sensor operative to sense the speed of the second drive wheel, a fifth sensor operative to sense the speed of the track belt, a sixth sensor operative to sense the operating pressure in the second hydraulic cylinder arrangement, a second hydraulic valve arrangement connected between the source of pressurized fluid and the second hydraulic cylinder arrangement, and the controller is operative to receive the signals from the fourth, fifth, and sixth sensors and determine the linear output speeds of the track belt and the drive wheel and deliver control signals to the second hydraulic valve arrangement to control the tension of the track belt in response to the difference in linear output speeds between the drive wheel and the track belt changing from a predetermined value. 
     
     
       9. The tension management system of claim 8 wherein the second hydraulic valve arrangement includes a third electrically actuated control valve connected to the hydraulic cylinder arrangement through a second supply conduit and a second pilot operated check valve is disposed in the second supply conduit between the third electrically actuated control valve and the hydraulic cylinder arrangement, a fourth electrically actuated control valve is disposed between the source of pressurized fluid and the pilot operated check valve, and a second drain conduit having an orifice disposed therein is connected between the reservoir and a point on the second supply conduit between the fourth electrically actuated control valve and the pilot operated check valve. 
     
     
       10. The tension management system of claim 9 wherein a second accumulator is connected to the second supply conduit adjacent the second hydraulic cylinder arrangement. 
     
     
       11. The tension management system of claim 3 wherein the hydraulic actuator arrangement includes a hydraulic cylinder having two separate piston chambers and the supply conduit is connected to one of the piston chambers and an accumulator is connected to the hydraulic cylinder and in communication with the other piston chamber. 
     
     
       12. The tension management system of claim 3 wherein the hydraulic actuator arrangement includes a hydraulic cylinder having the one end connected to the source of pressurized fluid operative to selectively lower the tension on the track belt and the other end connected to an accumulator operative to increase the tension on the track belt. 
     
     
       13. The tension management system of claim 2 wherein the control valve also selectively controls the fluid flow from the one end of the hydraulic cylinder arrangement to the reservoir and includes a second control valve operative to proportionally control the flow of pressurized fluid through a second supply conduit to and from the other end of the hydraulic cylinder arrangement.